Prefabricated buildings

ABSTRACT

A structural unit for, a transportable prefabricated room element used in the construction of buildings comprises a prefabricated floor panel and rigidly attached to one or each of two opposite ends of the panel, an upstanding, prefabricated, load-bearing end structure. There is a gap between the end structure and the adjacent end of the floor panel which is occupied by a set or hardened filling (e.g., mortar or metal) and the end structure is rigidly fixed to the panel by tie rods which extend within the latter into holes in the end structure and are anchored to the end structure. In the case of two end structures, at opposite ends of the floor panel, the tie rods extend through the panel and connect the two end structures together. The unit is made, preferably in accordance with U.S. Pat. No. 3,416,273, by effecting relative movements between the floor panel and end structure to enter the tie rods into the holes in the latter but leaving a gap between the end of the panel and the end structure, reducing the gap to its final dimensions, introducing the setting filling into the gap before or after the latter is reduced to its final dimensions, and anchoring the ends of the tie rods to the end structure.

United States Patent 1 Griissl et al.

[ 1 Oct. 2, 1973 PREFABRICATED BUILDINGS [73] Assignee: Elcon A.G., Zug, Switzerland [22] Filed: Jan. 12, 1971 [21] Appl. No.: 105,835

[30] Foreign Application Priority Data Jan. 17, 1970 Great Britain 2,398/70 [52] US. Cl. 52/741, 52/223 [51] Int. Cl. E04c 3/20 [58] Field of Search 52/438, 442, 741,

[56] References Cited UNITED STATES PATENTS 446,511 2/1891 Daly 285/284 2,075,633 3/1937 Anderegg 52/229 3,111,569 11/1963 Rubenstcin... 52/DIG. 7 3,319,387 5/1967 Stewing 52/227 3,473,273 10/1969 Gunkel 52/79 Primary Examiner-John E. Murtagh Attorney-Brumbaugh, Graves, Donohue & Raymond [57] ABSTRACT A structural unit for, a transportable prefabricated room element used in the construction of buildings comprises a prefabricated floor panel and rigidly attached to one or each of two opposite ends of the panel, an'upstanding, prefabricated, load-bearing end structure. There is a gap between the end structure and the adjacent end of the floor panel which is occupied by a set or hardened filling (e.g., mortar or metal) and the end structure is rigidly fixed to the panel by tie rods which extend within the latter into holes in the end structure and are anchored to the end structure. In the case of two end structures, at opposite ends of the floor panel, the tie rods extend through the panel and connect the two end structures together. The unit is made, preferably in accordance with US. Pat. No. 3,416,273, by effecting relative movements between the floor t panel and end structure to enter the tie rods into the holes in the latter but leaving a gap between the end of the panel and the end structure, reducing the gap to its final dimensions, introducing the setting filling into the gap before or after the latter is reduced to its final dimensions, and anchoring the ends of the tie rods to the end structure.

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I EMS, @Mwr W hm'w T a (wave PREFABRICATED BUILDINGS This invention relates to prefabricated buildings having at least one storey which comprises transportable prefabricated room elements as hereinafter defined, and to the construction of structural units for use in the manufacture of such room elements.

The expression transportable prefabricated room element is employed herein to define a transportable prefabricated cell-like structure haveing two opposed sides and two opposed ends constituting four faces of the cell, and comprising a floor panel, and preferably a roof or ceiling, and a vertical load-bearing end structure at each end of the floor panel and rigidly connected thereto for supporting parts of the building (such for example as the roof or ceiling, or the floor panel of a superimposed room room element) extending over and positioned above the floor panel, which room element is adapted to be mounted side-by-side, or end-to-end, or end-to-side, with a further room element in building up a storey of a building from a plurality of such elements. The expression end structure includes a wall, and also includes a vertical column, and a structure comprising spaced vertical columns which may be initially separate from each other. The said spaced columns may support fill-in panelling to'close or partly close an end or side of the room element and the expression fill-in panelling includes a wall panel, a door, or a window, and in the case of the wall panel the latter may be integral with two columns between which it extends or may be attached to them. If one or each end structure comprises two columns, the latter are desirably spaced apart by a distance which is at least sufficient to permit a door or window to be accommodated between them. Such room elements and buildings incorporating them are disclosed in British Pat. Nos. 1,027,241, 1,027,242 and 1,034,101 and US. Pats. Nos. 3,377,755, 3,416,273, 3,473,273, and 3,460,308.

An object of the present invention is a rigid structural unit incorporating the floor panel and the end structure or structures which unit is adapted to be incorporated in a transportable prefabricated room element. Another object of the invention is a method of joining each end structure to the floor panel.

U'.S. Pats. Nos. 3,377,755 and 3,473,273 disclose various ways of making the joint between a prefabricated floor panel and a prefabricated end structure, some of which involve the use of an adhesive such as an adhesive cement of an epoxy resin. These procedures have a certain drawback. The first is the relatively long period required for the setting of the adhesive cement in the joint: this leads to a bottle-neck in the manufacture of room elements and a corresponding increase in cost and a reduction in output per square foot of floor area in the assembly hall where the room panel and an upstanding, prefabricated, load-bearing end structure rigidly attached to at least one end of the panel with a gap between the structure and the adjacent end of the panel which gap is occupied by a set or hardened filling, wherein the panel is provided with tie members (e.g., tie rods) which extend within it and the ends of which tie members protrude from the panel end into holes (or channels) in the structure and are anchored to the latter, desirably with the tie members under tension.

Preferably the end structure is connected to the end of the panel, at each of two locations spaced apart widthwise of the panel, by two said tie members which are spaced apart heightwise of the structure. This ensures that a force applied to the end structure and tending to alter its angle with the panel, will always be resisted by differential tension in the tie members and differential compression in the filling.

Each tie member may extend within the panel for a part only of the length of the panel, with its inner end anchored within the panel. Alternatively, in a unit having an end structure rigidly attached to each end of the panel, the tie members may extend completely through the panel to connect the end structures.

The invention further provides in the manufacture of a structural unit in or for a transportable prefabricated room element as hereinbefore defined, which unit comprises a prefabricated floor panel and an upstanding, prefabricated, load-bearing end structure rigidly attached to at least one end of the panel by tie members extending within the panel and having ends protruding into and secured within holes (or channels) in the end structure, a method of making the joint between the panel and end structure which comprises: (a) effecting such relative movement between the panel and end structure as will enter the tie members into the holes but leaving a gap between the end of the panel and the structure, (b) introducing into the gap a setting filling the thickness of which when set fixes the final width of the gap, (0) placing the tie members under tension while holding the panel and end structure in a fixed position, and (d) after the filling has set, anchoring the end of the tie members in the end structure so that the latter is biased towards the end of the panel.

The tension should be at least sufficient to hold the joint firm and to prevent the filling from being stressed in tension.

One embodiment of this method comprises the sequential steps of (a) effecting such relative movement between the end structure and panel as will enter the tie members into the holes but leaving an over-size gap between the end structure and the adjacent end structure of the panel, (b) introducing the setting filling into the over-size gap, (0) adjusting the panel and structure to their final positions and thereby narrowing the gap to its final width, (d) holding them in their final positions while the filling sets or hardens, and (e) anchoring the tie members under tension to the end structure.

In a modified method, the gap may be brought to its final width before the setting filling is introduced into it.

Important subsidiary features of the invention are the acceleration of the setting of the filling by heat supplied by a resistance-heating element buried in it, or by an external high frequency generator, or the use of a quick-freezing metal as the filling, the molten metal being introduced into the gap after the latter has been brought to its final width.

In order that the invention may be better understood reference will now be made to the accompanying drawing, in which:

FIG. 1 is a sectional elevation through adjacent parts of the floor panel and end structure showing the joint;

FIG. 2 is a view similar to FIG. 1 showing a modified joint;

FIG. 3 is a section taken on the line 33 in FIG. 2;

FIG. 4 is a sectional'elevation of a further joint;

FIG. 5 is an elevation of the end structure looking from the left in FIG. 4;

FIG. 6 is a sectional elevation showing a still further joint;

FIG. 7 is a perspective view of the lower part of the structure in FIG. 6;

FIG. 8 is a perspective view of one corner of a floor panel and the adjacent column of an end structure, and illustrates the use of high frequency heating;

FIG. 9 is a perspective view of one end of a structural unit according to this invention; and

FIG. 10 is a perspective view illustrating the fabrication of the structural unit in ajig according to US. Pat. No. 3,460,308.

In FIG. 1 there is shown in vertical section a representative end portion of a precast reinforced concrete floor panel 1 and a precast reinforced concrete end structure 2. Component 2 is representative of a wall which extends across the end of the floor panel or one of a pair of vertical loadbearing pillars or columns located adjacent opposite corners of that end of the panel.

It is here pointed out that in general in all units according to the present invention there will be a structure or structures 2 at each end of the floor panel I, the joint or joints at each end being as described and illustrated herein. If the end structure consists of a loadbearing column or columns, each thereof is fixed at its base to the panel. If the structure comprises two columns, these two may be initially separate, or may be connected by an integral cross-member or beam or by an integral fill-in panel. FIG. 9 shows an end structure 2 consisting of two vertical columns 2a and an integral cross beam 2b.

In FIG. 1 there is a pair of joint elements each of which consists of a screw-threaded rod 3 precast into the floor panel 1 by means of an anchoring element or abutment 4 to which the buried end of the rod is fastened by a nut 5. Corresponding anchoring elements or abutments 4 are precast into the structure 2. It will be seen that the rods 3 are spaced apart in the vertical direction within the thickness of the panel 1.

For the major part of its length within the panel, each rod 3 extends through a tube (or channels) 6 which is precast into the floor panel. The rods 3 protrude from the end face of the panel 1 and are received in clearance holes (or channels) in the structure 2 which are defined by tubes 5 precast into the component and leading to the elements 4.

The elements 4 and 4' need not be welded or otherwise fixed to the reinforcements (not shown) of the panel I and structure 2. It is sufficient that some of the reinforcements surround the elements 4, 4 in a well understood manner so that the concrete in the zone between the reinforcements and the elements 4, 4' respectively is stressed in compression when transmitting any tension forces in the rods 3 to the elements 4, 4.

When the structural unit is assembled, the structure 2 and the floor panel are moved relatively in the general plane of the latter until the protruding ends of the rods 3 enter the tubes 5 and the anchorage elements 4', rubber sealing rings 8 having first been placed around the rods. A gap 9 is left between the end of the floor panel 1 and the face of the structure 2, its width at this stage being greater than its final width. This gap is occupied by a layer of dry mortar 9' which may be applied to the panel 1 and structure 2 while they are still separated or may be subsequently introduced into the gap 9. The component 2 is thereupon moved into its predetermined final position in which it is held rigidly until the mortar is hardened to a compressive strength, of for example, about Kg/cm This may take about one hour.

Once the mortar has hardened sufficiently, nuts 10 are screwed onto the ends of the rods 3 within pockets 11 in the structure 2 and are tightened so as to place the rods under a certain degree of tension. In order to protect the nuts the cavities are filled with a plastic or other suitable filler 11'. A grouting or setting filling of cement slurry (preferably of a composition which will expand slightly on setting) is injected through the injection tubes 7 into the clearance between the interior of tubes 6 and 5 and the rods.

The chief difference between the construction shown in FIG. 1 and that shown in FIGS. 2 and 3 is the replacement of the rods 3 by the post-tensioning rods 12 which traverse the floor panel 1 in the longitudinal direction from end to end and are not fixed to the reinforcement. They are provided, in a manner known per se, with a coating which delays a firm bond between the rods and the surrounding concrete for, say, one or two weeks until after the post-tensioning has been carried out. Alternatively the rods 12 can be laid as in FIG. 1, in tubes (or channels) which are cast into the floor panel and which are filled with a cement slurry after post-tensioning. As will be seen from FIG. 2 the rods 12 are slightly inclined upwards towards their ends (which are received in clearance holes 14 in each end structure 2). This produces, after post-tensioning, a more favourable stress distribution in the panel 1 when the latter is loaded. The assembly procedure is substantially the same as described in relation to FIG. 1. but a difference is that the cement slurry is injected from the side through a tube or tubes 13 (FIG. 3) into the cavities (or clearances) between the rods and the concrete of the structure 2. Another difference is that instead of the rods being tightened by means of nuts as in FIG. 1 they are post-tensioned by means of jacks, not shown, and are secured by wedges or split collets 15 in the retaining rings 16. Holes 17 in the rings provide vents allowing the air to escape during the injection of the slurry.

In both the foregoing embodiments the metal rods, which transmit any tension forces between the floor panel and the end structure, are positively secured in both. These forces are not transmitted across a weld or across an adhesive cement layer stressed in shear, and the joints are therefore safe and fireproof.

However, both of the foregoing embodiments suffer from the drawback that, after assembly, a considerable time must elapse until the dry mortar in the gap 9 has hardened.

This drawback is overcome by each of the two methods which are illustrated in FIGS. 4 and 5 and in FIGS.

6 and 7 respectively as applied to the joint shown in FIGS. 2 and 3. It is to be appreciated however, that these methods can equally well be applied to the joint shown in FIG. I.

In FIGS. 4 and 5 a resistance-heating element comprising an electrically conducting mesh 25 cut to size is introduced into the gap where it is position by the rubber rings 26. This mesh may consist of galvanized wire rods; e.g., welded wire rods 1mm in diameter at a pitch of 12 X 12mm. When the assembly has been completed as above described, the top and bottom ends of the mesh are suitably connected at 18 and 118' to an electrical power supply which heats the wires and therefore greatly shortens the setting time of the mortar filling the gap. Good results have been obtained by applying power at about 3Kw and a voltage between 4 and 8. A very suitable mortar consists of:

a mixture of 90 percent by weight refractory grog of 0 to 0.6mm grain size and I0 percent by weight clay, to which mixture is added 2 percent by weight sodium silicium flouride (Na Si mixed into a sufficient quantity of sodium water glass to give it the desired consistency for injection.

Under these conditions the setting time is reduced from at least one hour to only about 15 minutes. After this time lapse the mortar is hard enough to take in compression the stresses imposed on it by the tension rods.

However, when the concrete of the floor panel and end structure (the faces of which are in contact with the mortar in the gap) is very cold less favourable results are obtained owing to heat loss to the concrete. Therefore two electrically conducting meshes may be employed, one in contact with or closely adjacent to each of the two faces, with the mortar sandwiched between them. Indeed, the sandwich may be prepared and, as such, inserted between the said faces before the rods are entered into the holes.

In this case the water content of the mortar can be reduced by reducing the amount of clay, say from percent to 6 percent, and reducing the water glass (or its water content) to a minimum to give a drier mix.

The alternative method illustration in FIGS. 6 and 7 is applicable to the joint shown in FIG. 1 and to that shown in FIGS. 2 and 3. A U-shaped resilient gasket 19 (of for example, neoprene rubber) is positioned at the middle region of the gap to define a cavity 20 through which the rings 26 extend. After the panel and end structure have been finally positioned as already described (i.e., after the gap has been reduced to its final width) a low melting alloy is poured into this cavity, which alloy freezes rapidly by loss of heat to the concrete faces of the gap. A relatively inexpensive and suitable alloy consists of lead with the addition of, for example, 4 percent antimony. Within about minutes the alloy cools and hardens to such an extent that it is capable of taking the tension forces exerted by the rods after post-tensioning, without yielding. As the yield point of the alloy may vary between 200 and 500 Kg/cm" according to the antimony content and the total area of the cavity must be adjusted accordingly. The volume of the gap other than that enclosed by the gasket 19 is filled with dry mortar as described above which will set in the course of the subsequent manufacturing stages. The alloy layer is thereby firmly insulated and fireproofed.

Turning now to FIG. 8 which illustrates the accelerated curing of the mortar joint 9' in the gap 9 between an end of the floor panel I and a pillar of the end structure 2, copper electrodes 21 connected to a highfrequency generator are applied to the components so as to close the vertical edges of the over-size gap and to act as shuttering for the mortar. The bottom edge of the gap is closed by a strip of adhesive tape 22. After the oversize gap has thus been sealed, hydraulic cement is introduced into it, the relative positions of the panel 1 and end structure 2 are adjusted to narrow the gap and to bring the unit to the desired linear and angular dimensions, and high frequency current is applied to accelerate the setting of the cement.

Best results are obtained with a high quality Portland cement, primarily that commercially available under the name Tricovit which is manufactured by Chemische Fabrik Grunau G.m.b.I-I of Illertissen, Bavaria, Germany. This product is described by the manufacturers as being a mixture of alumina cement and other unspecified cements. For the purposes of the present invention the said product is to be mixed with sand (0 to 2 mm grain size) and water to form a dry mortar. A suitable mix is 150g Tricovit 222g sand (grain size 0.2mm). (at 8.2% moisture content cira I50 c.c. water) 40g water A compressive strength of kg/cm after 10 minutes curing time is desirable, and the following is the specifi cation of a suitable high frequency generator:

Type BBC 10 C 12 (Brown-Boveri product) Output l0 kw Frequency l3.6 MHZ lnput 380 V 50 CPS 3-Phase Full load demand 19 kw.

In practice the area of the void (between the base of each column or pillar 2a and the end face of the floor panel) is 220 X 350 mm and its width is about 10mm.

The assembly and positioning of the floor panel and each end structure may be carried out by the method and by use of a jig which forms the subject of US. Pat No. 3,460,308.

This is illustrated in FIG. 10, which is a view corresponding to FIG. 1 to that Patent and shows the fabrication, in the jig, of a structural unit comprising the floor panel l and an end structure 2 rigidly attached to each end of the panel at the base of each vertical column 2a. A high frequency generator is shown at 24, supplying electrodes 21 (FIG. 8) through leads 28. The manner in which the end structures and panel are relatively positioned by the jig, while they are being permanently connected in such manner that all linear and angular dimensions of the finished units have a high degree of accuracy irrespective of the manufacturing tolerances of the three components will be appreciated from the said Patent. However it may be pointed out that each end structure can be adjusted along the protruding ends of the tie rods to positions determined by limit stops in the jig, and the fact that said protruding ends are received in clearance holes in the end structures permits the heightwise and widthwise location of the end structures in relation to the panel, and the angular attitude of each end structure in its own plane and also in relation to the surface of the panel, also to be fixed by limit stops in the jig. The fact that the cavities between the rods and the clearance holes are grouted with cement assists in retaining the said location and angular attitude.

For the subsequent method of constructing room elements, in which the units form the main load-carrying components, at a factory and the transport of the room elements to a building site and their erection at that site into a building or storey ofa building, reference may be made to US. Pat. Nos. 3,377,755 and 3,416,273.

What is claimed is:

1. A method for the manufacture of a structural unit for a transportable prefabricated room element, the structural unit comprising an unstressed prefabricated floor panel, a plurality of tie members positioned freely in channels in the floor panel and protruding therefrom, and at least one upstanding, prefabricated, loadbearing end structure, the end structure having a plurality of channels therein for mating with the protruding tie members, the method comprising the steps of:

a. mating the floor panel and the end structure, the

tie members protruding from the floor panel being positioned in corresponding channels in the base of the end structure,

b. positioning the mated floor panel and end structure so that a predetermined gap is left between the adjacent surfaces thereof,

. rigidly fixing the relative positions of the mated floor panel and end structure,

. filling the gap with a setting filler,

. applying tension to the tie members,

. allowing the filler to set,

. releasing the mated floor panel and end structure from the fixed position, h. anchoring the tensioned tie members, and

i. rigidly securing the tie members to the floor panel and the end structure by inserting a setting filler into the channels in the floor panel and the end structure.

2. The method of claim 1 further comprising the step of heating the setting filler in the gap in order to accelerate the setting of the filler.

3. The method of claim 2 wherein the filler in the gap is heated by means of electrodes positioned in the gap.

4. The method of claim 1 further comprising the step of applying a high frequency current to the filler in the gap in order to accelerate the setting of the filler.

5. The method of claim 1 further comprising the step of positioning retaining means in the gap, the retaining means defining a cavity, and filling the cavity with the setting filler.

6. The method of claim 1 wherein the setting filler is mortar.

7. The method of claim 1 wherein the setting filler is a quick setting metal.

8. The method of claim 1 wherein the tie members are positioned in channels in the floor panel and, subsequent to the tensioning and anchoring of the tie members, the channels in the floor panel are filled with a setting filler.

9. The method of claim 1 wherein the gap is filled with a setting filler before the relative positions of the mated floor panel and end structure are rigidly fixed.

10. The method of claim 9 further comprising the step of adjusting the width of the gap to a final predetermined width after the gap is filled with a setting filler.

11. A method for the manufacture ofa structural unit for a transportable prefabricated room element, the structural unit comprising an unstressed prefabricated concrete floor panel, and at least one upstanding, prefabricated, load-bearing concrete end structure, the end structure having a plurality of channels therein, the method comprising the steps of:

a. coating a plurality of tie members with a material which delays a firm bond between concrete and the tie members,

b. positioning the plurality of tie members in the floor panel, the tie members being positioned so that at least one end of each protrudes from the floor panel,

c. mating the floor panel and the end structure, the tie members protruding from the floor panel being positioned in coresponding channels in the base of the end structure,

d. positioning the mated floor panel and end structure so that a predetermined gap is left between the adjacent surfaces thereof,

e. rigidly fixing the relative positions of the mated floor panel and end structure,

f. filling the gap with a setting filler,

g. applying tension to the tie members,

h. allowing the filler to set,

i. releasing the mated floor panel and end structure from the fixed position,

j. anchoring the tensioned tie members,

k. rigidly securing the tie members to the end structure by inserting a setting filler into the channels, and

1. allowing the coating on the tie members to firmly and rigidly bond the tie members to the concrete floor panel. 

1. A method for the manufacture of a structural unit for a transportable prefabricated room element, the structural unit comprising an unstressed prefabricated floor panel, a plurality of tie members positioned freely in channels in the floor panel and protruding therefrom, and at least one upstanding, prefabricated, load-bearing end structure, the end structure having a plurality of channels therein for mating with the protruding tie members, the method comprising the steps of: a. mating the floor panel and the end structure, the tie members protruding from the floor panel being positioned in corresponding channels in the base of the end structure, b. positioning the mated floor panel and end structure so that a predetermined gap is left between the adjacent surfaces thereof, c. rigidly fixing the relative positions of the mated floor panel and end structure, d. filling the gap with a setting filler, e. applying tension to the tie members, f. allowing the filler to set, g. releasing the mated floor panel and end structure from the fixed position, h. anchoring the tensioned tie members, and i. rigidly securing the tie members to the floor panel and the end structure by inserting a setting filler into the channels in the floor panel and the end structure.
 2. The method of claim 1 further comprising the step of heating the setting filler in the gap in order to accelerate the setting of the filler.
 3. The method of claim 2 wherein the filler in the gap is heated by means of electrodes positioned in the gap.
 4. The method of claim 1 further comprising the step of applying a high frequency current to the filler in the gap in order to accelerate the setting of the filler.
 5. The method of claim 1 further comprising the step of positioning retaining means in the gap, the retaining means defining a cavity, and filling the cavity with the setting filler.
 6. The method of claim 1 wherein the setting filler is mortar.
 7. The method of claim 1 wherein the setting filler is a quick setting metal.
 8. The method of claim 1 wherein the tie members are positioned in channels in the floor panel and, subsequent to the tensioning and anchoring of the tie members, the channels in the floor panel are filled with a setting filler.
 9. The method of claim 1 wherein the gap is filled with a setting filler before the relative positions of the mated floor panel and end structure are rigidly fixed.
 10. The method of claim 9 further comprising the step of adjusting the width of the gap to a final predetermined width after the gap is filled with a setting filler.
 11. A method for the manufacture of a structural unit for a transportable prefabricated room element, the structural unit comprising an unstressed prefabricated concrete floor panel, and at least one upstanding, prefabricated, load-bearing concrete end structure, the end structure having a plurality of channels therein, the method comprising the steps of: a. coating a plurality of tie members with a material which delays a firm bond between concrete and the tie members, b. positioning the plurality of tie members in the floor panel, the tie members being positioned so that at least one end of each protrudes from the floor panel, c. mating the floor panel and the end structure, the tie members protruding from the floor panel being positioned in coresponding channels in the base of the end structure, d. positioning the mated floor panel and end structure so that a predetermined gap is left between the adjacent surfaces thereof, e. rigidly fixing the relative positions of the mated floor panel and end structure, f. filling the gap with a setting filler, g. applying tension to the tie members, h. allowing the filler to set, i. releasing the mated floor panel and end structure from the fixed position, j. anchoring the tensioned tie members, k. rigidly securing the tie members to the end structure by inserting a setting filler into the channels, and l. allowing the coating on the tie members to firmly and rigidly bond the tie members to the concrete floor panel. 